Chemistry Production of Materials Notes
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1. Fossil fuels provide both energy and raw materials such as ethylene, for the production of other substances 1) Construct word and balanced chemical equations of chemical reactions as they are encountered • Methane + oxygen carbon dioxide + water • CH4(g) + 2O2(g) CO2(g) + 2H2O(l) 2) Identify the industrial source of ethylene from the cracking of some of the fractions from refining of petroleum Generally, demand for petrol exceeds supply produced from fractional distillation of crude oil. Thus, oil refineries increase the proportion of the desired hydrocarbon (ie ethylene) by converting lower demand fractions. This process is called catalytic cracking. Catalytic Cracking: process where high molecular weight fractions from crude oil are broken into lower molecular weight compounds. 3) Identify that ethylene, because of the high reactivity of its double bond, is readily transformed into many suitable products The two bonds of ethylene are not identical. The second bond (pi-bond) is weaker than the first bond (sigma-bond). Thus, only a small amount of energy is needed to enter the system in order to convert a double bond into a single bond. This results in ethylene’s high reactivity. 4) Identify that ethylene serves as a monomer from which polymers are made • • • Ethylene is polymerised to polyethylene High pressures produce soft, low density polyethylene, consisting of tangled chains (with molecular masses 100,000)
5) Identify polyethylene as an addition polymer and explain the meaning of the term Addition polymerisation: a process in which many identical small molecules combine to form one large molecule, with no by-products. The small molecules are called monomers, while the large molecule is called a polymer.
H C C H H
H C
H C H
n
H
H
n
In addition polymerisation, no other products are formed. 6) Outline the steps in the production of polyethylene as an example of a commercially and industrially important
1. Fossil fuels provide both energy and raw materials such as ethylene, for the production of other substances 1) Construct word and balanced chemical equations of chemical reactions as they are encountered • Methane + oxygen carbon dioxide + water • CH4(g) + 2O2(g) CO2(g) + 2H2O(l) 2) Identify the industrial source of ethylene from the cracking of some of the fractions from refining of petroleum Generally, demand for petrol exceeds supply produced from fractional distillation of crude oil. Thus, oil refineries increase the proportion of the desired hydrocarbon (ie ethylene) by converting lower demand fractions. This process is called catalytic cracking. Catalytic Cracking: process where high molecular weight fractions from crude oil are broken into lower molecular weight compounds. 3) Identify that ethylene, because of the high reactivity of its double bond, is readily transformed into many suitable products The two bonds of ethylene are not identical. The second bond (pi-bond) is weaker than the first bond (sigma-bond). Thus, only a small amount of energy is needed to enter the system in order to convert a double bond into a single bond. This results in ethylene’s high reactivity. 4) Identify that ethylene serves as a monomer from which polymers are made • • • Ethylene is polymerised to polyethylene High pressures produce soft, low density polyethylene, consisting of tangled chains (with molecular masses 100,000)
5) Identify polyethylene as an addition polymer and explain the meaning of the term Addition polymerisation: a process in which many identical small molecules combine to form one large molecule, with no by-products. The small molecules are called monomers, while the large molecule is called a polymer.
H C C H H
H C
H C H
n
H
H
n
In addition polymerisation, no other products are formed. 6) Outline the steps in the production of polyethylene as an example of a commercially and industrially important